First upgrade takes about 150 Gold and somewhat 100 - 150 Mana, for what? 5 gold per 2 - 3 seconds? Unless you're turtling for 40 minutes straight, I don't think it's gonna help you much! :(

Yes, it's worth it.
Level 3 passive gold is 20 gold every 10(?) seconds and so much mana every couple of seconds. It's very useful.

i find it completely useless, the only time i buy it is when i own the middle pillar and have my 8 miners

I think it's only worth getting when you have nothing else to buy. An extra miner is always going to be more economical than passive income.

It's also only worth getting passive income if you're gonig to get all 3 levels (the third one has twice the value of the first two upgrades)

Passive income is very helpful in campaign, but not much in online

maybe they should decrease the first upgrades cost, keep the middle upgrades cost, and increase the last upgrades cost just a bit

so it works with you, not against you

I only buy it on GH if I ever do. TBH I think it could use a buff or a rework.

I never really use it much, does it really help much at all, to be spending that much on Passive?

Really, consider the points. You get it early game, that puts you down economically. You need to make up for it and by then your opponent's army/economy will have surpassed yours.

You get it late game:
There is no point. At that point, you will have enough miners and it's not necessary at all.

Quote from ShadowyWhisper

I never really use it much, does it really help much at all, to be spending that much on Passive?

Really, consider the points. You get it early game, that puts you down economically. You need to make up for it and by then your opponent's army/economy will have surpassed yours.

You get it late game:
There is no point. At that point, you will have enough miners and it's not necessary at all.

Well, passive income helps if the opponent has middle.

Sincerely, Fr0st.

Even out the middle tower.

Well, I think its completely useless, and I dont use it at any time, well the truth is that from the strated game I have never used passive income and I dont wanna waste money on that,

Its better in terms of 'investment to return' to buy extra miners rather than passive income. And in those terms alone, 'no passive income is not worth it'.
But thats an incomplete picture and therefore misleading. (See the exampe of logic based on an incomplete picture below if thats not obvious).

The other factors are that
1. you dont have to put any population cost towards the return of both gold and mana, where as miners cost population and so reduce the military you can build (i.e. you get a bigger military if you invest in passive income 3 than if you invest the same costs in miners - which is huge once you reach population cap.)
2. you cant have the income killed or stopped if the enemy attacks your base. If he kills your miner, or forces you to garison, your miner is not as good an investment as you thought.
3. your income continues when the gold reserves have been used up. If your in a longer game, often the first line of gold is finished, which reduces the number of miners that can work gold - if both players are in the same state, having passive income may be a huge benifit as you have a better economy than him, and you have the population slots free too.

So the complete answer has to be there are some good reasons to buy passive income, and in some situations its a good idea - and if you do so, its better to buy all three than just 1 or 2 levels as the return is better. So; dont screw your early military or economy to rush for it, hiner hustle is a better early buy. But dont ignore it mid game if you have income to spare.

Passive income are good, except it's first level when it sucks.
Info on getting resources:

Middle Tower: 2 Miners gone to gold.
Miner's Hustle: 1.5x production of your miners
Passive Gold Income 1: 0.5x a miner
Passive Gold Income 2: 1.0x a miner
Passive Gold Income 3: 2.0x a miner

So, in ascending order, which should I research first?